A lighting device that uses a light emitting diode (hereinafter referred to as LED) has a large number of LEDs. To the LEDs, a driving current is fed to cause them emit light to illuminate as a lighting device. When a forward supply voltage to each of the LEDs used in the device as the light source is increased gradually from a state of approximately zero volts, the LED begins to pass a current at the prescribed voltage of VLC (V) and light emission starts. Further increase in the supply voltage causes the current flowing through the LED to increase, and the light emission amount of the LED increases.
LEDs, unlike ordinary diodes, have a large forward voltage drop, which invite large power consumption. The power is consumed not only for light emission, but in addition a considerable portion of the power uselessly escapes as the heat loss causing rise in the temperature of LEDs.
If temperature of the LED rises due to heat generation of LED, there arises a danger of ignition of dusts, and in addition the life of the LED is adversely affected. Therefore, a heat dissipation arrangement of metallic material having an excellent thermal conductivity is provided. This arrangement dissipates heat that the LED generates and suppresses, thereby, the temperature rise of the LED. For example, Japanese Patent Application Laid-open No. TOKKAI 2012-69303 (Patent Literature 1) has disclosed a technique, wherein a metal pedestal 30 having heat dissipation effect is provided in a straight tube 10 and fire heat generated from an LED module 20 is dissipated thereby to suppress the temperature rise of the LED module 20.